Photographic film



Patented Aug. 14, l928,

UNITED sures FRANK FORS'IER RENWICK, OF

PATENT OFFICE.

PARLIN, NEW JERSEY, ASSIGNOB, BY MESNE AS- SIGNHENTS, T0 DU PONT-PATEE FILM MANUFACTURING CORPORATION, OF WIL- MINGTON, DELAWARE, A CORPORATION 01 DELAWARE.

PHOTOGRAZPHIG FILM.

Application filed August 20, 18%. Serial No. 51,507.

This invention relates to photographic film and particularly to film of the so-called non-static type. In the motion picture art particularly, trouble is experienced with stal tic electrical charges onthe film which are, forexample, frictionally generated when the film is run rapidly through cinematographic apparatus. These charges, if not counteracted in some way, cause markings on the F film and may, indeed, cause fire. The resent invention has to do with a film whic by virtue of its construction, overcomes, or rather, eliminates static difiiculties of the character mentioned. It is the object of the invention to provide a him having; the men tioned, and other, desirable characteristics.

Because of its strength, ease of working,

vailability, and so on, it is desirable that us should be primarily oi cellulose nitrate.

d1 culty: with this material is, however, at strongly charges electrically in use,

re n negatively. in accordance sent invention there used with t l -b-le nitrocellulose body another pelll 1 composition which charges rive Tlhis composition is preferably lied backing,

Furthermore, the bee is such that it is,-'lor practical goo see, insoluble in the baths and res against scratching or other damage 'lPhus the invention provides film which, although it is f9rimarily of nitrocellulose is non-static and is at the same time not adversely affected by baths and so on l l 'ithout restricting *he invention thereto, film embodying it is shown in the 0lC3 Oll1- yi-anying drawinm in the drawing, which. is conventional, exaggerated, cross-sectional view, the emulsion is indicated at body at 2, and the bashing 3, the sing; constituted as indicated by the applied ilfiltfi,

1" comprise cellulose nitrate and. ein which electrilios positively as, for ex J le, casein, gelatin, albumen, keratin, e

l "oteins such'as aeiu, r cor ce" ulose acetate proteins. in, where substance used with the water soluble, the presence oi the wateniusolulole ir redient prevents, for practical purposes, shooting of the backing by the baths, I have found. In notably that of casein, whenthe anti-static substance is. insoluble, the protein may be used alone as a. layer or backing. Afiln'i body is ordinarily, of course, used to carry a sensitized emulsion. This emulsioncom= prises gelatin, so that, when carrying the emulsion, the present film comprises a cone tral nitrocellulose negative layer with a positwo layer on each side thereof.

The general methods of casting film'and applying bookings are, of course, Well-known and need not be'here described in detail; but as illustrating the invention, Without how ever confining it to the examples given, the iollowing formulas are given (1) Casting dope for forming a body to which emulsion, and bookings ot'the present invention, may be applied :-Nitrocellulose loll; acetone 80; camphor 2; iusel oil 25 {parts by weight}.

Acqueous casein backho solution Seal: 30 grams of casein overnight in 100 cc.

water to which has been added 15 cc. of concentrated ammonia solution. water to bring the volume up to 1500 cc. W rm to 100 F. and filter through a line clot-h, lt or'use this solution should be diluted with from to 100 times its volume of water. With less than fold dilution it is apt to give smeary bookings; with Q00 times dilution its ell'ect is not usually sufficientl strong to be useful.

(3) l/lixed-solvent casein backing; solu tion:-Soak grams of casein in 15 cc. of concentrated ammonia plus 1725 cc. water. Vlarm to about F. cool, and add cc. of denatured ethyl alcohol, then add 11825 cc. of methyl alcohol with stirring followed by 1500 cc. of acetone.

tel) Backing solution containing cellulose acetate and elatin :Prepare the following A and B solutions and add A. to B while stirring thoroughly. Solution Ar acetone-soluble cellulose acetate 5 grams;

I acetone 225 00,; benzyl alcohol 520 cc. Sold tion ldi Dissolve 5 grams of hard photographic gelatin in a. solution of 2 gs. out acetic acid. in'5 cc. 'methyl alcohol plus 5 cc. water, with gentle warming, and add this solution to 220 cc. of methyl alcohol.

g5) Backing solution containing 'nitrocehulose and gelatin-:Dissolve by gentle certain cases,

warming grams of gelatin in a mixture salt, say potassium nitrate, as will be underof, acetic acid 12 ms, water 66 rams, denatured ethyl alco 01 60 grams. A d 360 grams of denatured ethyl alcohol. Then add the solution to 4164 grams of denatured ethyl alcohol, and finally add 1680 grams of acetone; Dissolve 12 grams of nitrocellulose in this mixture.

(6) For a backing solution containing casein and cellulose nitrate or acetate, a solution of the cellulose ester in compatible solvents may be .mixed with solution 3, the respective amounts being varied as desired having regard for the general consideration, illustrated by formulas 4 and 5, that in those cases where a cellulose ester is used in conjunction with a protein the solvent must be such as will dissolve the ester without precipitating the protein in the concentrations employed.

In addition to the possibilities indicated above, it will be evident that a backing solution may comprise more than one protein, such solution being repared, say, by mixing suitable solutions 0? the proteins, as casein and gelatin. Also, of course, more than one protein may be used in conjunction with one or more cellulose esters.

As will be plain to those skilled in the art, all backings are applied in solution form by means of a roller dipping in .a trough in one or other of the customary manners, and solvents evaporated. The backing layer is excessivel thin, only about 6 pounds of the solution employed being required for square feet of film base. The backing is substantially neutral and has no efiect upon the emulsion when the film is rolled.

Regarding the degree of esterification of the cellulose esters employed, the nitrate may contain from 9 to 12.5 per cent. nitrogen, and the acetate from 52 to 58 per cent. acetyl. As to the gelatin, the purest commercial photo aphic gelatin is satisfactory. This elatin l have found, is more conductive t an cellulose nitrate or acetate.

In using the casein, it is desirable to have the backing la er thin to avoid the possibility of clou ess. Thin layers are, of course, obtained by using dilutesolutions. Furthermore, by using nitrocellulose or acetyl cellulose in the same solution with the casem there is provided a further guard against cloudiness Should it for any reason he desired, ma-

terials for increasing the electrical 'conductivity of the baekin may be employed, such 8. material being, or instance, a metallio stood.

For the sake of brevity in the claims I, on occasion, employ the terms positive and negative as indicating that the materials mentioned will develop a positive or negative electrical charge when acted on frictionally. The degree to which the opposite charges counteract each other. and the extentto which film is fully non-static will, of course, depend on various conditions, but, in any case, the combination of positive and negative materials is highly advantageous.

This 15 a companion case to my United States application Serial No. 51,508, for photographic film, filed August 20, 1925.

I claim:

1. A photographic film including a body layer comprising cellulose nitrate, and a layer comprising a cellulose ester and a p10- tein.

2. A photographic film including a body layer comprising cellulose nitrate, and a layer comprising a cellulose ester and a protein ositively electrifiable with respect to cellu ose nitrate.

3. A photographic film including layer comprising cellulose nitrate, layer comprising cellulose nitrate protein.

4. A photographic film including layer comprising cellulose nitrate, layer comprising cellulose nitrate protein positively electrifiable with to cellulose nitrate.

5. A photographic film including a body layer comprising cellulose nitrate, and a layer comprising cellulose nitrate, cellulose acetate, and a protein.

6. A photographic film including a body layer comprising cellulose nitrate, and a layer comprising cellulose nitrate, cellulose acetate, and a protein ositively electrifiable with respect to cellu ose nitrate.

7. A photographic film including a body layer of cellulose nitrate, and a backing comprisin cellulose nitrate and gelatin.

8. hotographic film including a body of cellu ose nitrate, and a backing comprisin cellulose nitrate, cellulose acetate and ge atin.

9. A photographic film including a body layer comprising cellulose nitrate, and a layer comprising casein and gelatin together with a cellulose ester.

In testimon whereof I afiix my signature.

FR FORSTER REN'WICK.

a body and a and a a body and a and a respect 

